JPH09143752A - Composition and treating bath for treating aluminum based metal surface and treatment thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a protective coating forming a film high in uniformity with a thin film, and good in appearance, corrosion resistance and adhessiveness. SOLUTION: In an aluminum based metal surface treating method, a treating bath is prepared by using a composition for aluminum surface treating containing at least one kind among phosphoric acid, condensed phosphoric acid and their salts, at least one kind of zirconate and titanate and at least one kind among fluoride, phosphorus acid, hypophosphorus acid or their salts, and the treating bath is brought into contact with the surface of the aluminum based metal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aluminum-based metal surface treating composition, a treating bath and a treating method, and in particular, it forms a thin film having high uniformity, and provides good appearance, corrosion resistance and coating adhesion. The present invention relates to an aluminum-based metal surface treating composition, a treating bath and a treating method for providing a coating.

[0002]

2. Description of the Related Art Conventionally, as a surface treatment method for aluminum and their alloys, a chromate treatment or an alumite treatment has been performed. However, chromate treatment has drawbacks such as environmental pollution, toxicity to the human body, and difficulty in disposing of wastewater treatment sludge.On the other hand, alumite treatment requires a large amount of equipment, consumes much power, and is not economical. Was.

[0003] In order to solve the above-mentioned disadvantages, various non-chromate treatment methods have been proposed. For example, “Coating solution for metal surface” in JP-B-56-33468 includes zirconium or titanium or a mixture thereof, and a phosphate (that is, a phosphate).
And an acidic aqueous coating solution containing a fluoride and a pH in the range of about 1.5 to about 4.0.

In Japanese Patent Publication No. 57-39314, "Aluminum surface treatment method", the concentration of one or more titanium salts or zirconium salts is 0.01 to 10 g / l in terms of metal, and the concentration is over. Hydrogen oxide concentration 0.005
5 g / l, and 0.05 to 20 g / l in terms of phosphoric acid containing one or more of phosphoric acid and condensed phosphoric acid.
And their weight ratios are 1 to 10: 0.1 to 1
A surface treatment method for aluminum and its alloys which is treated with an acidic aqueous solution containing 0: 1.5 to 30 has been proposed.

The above-mentioned “Coating solution for metal surface” disclosed in JP-B-56-33468 and JP-B-57-393.
No. 14, "Surface treatment method for aluminum" can be used, for example, when a surface of a beverage aluminum container made of aluminum or an aluminum alloy is coated with a protective film.

[0006] Usually, aluminum containers for beverages made of aluminum or aluminum alloy are made of drawing or aluminum.
It is manufactured by a molding operation called AND ironing (hereinafter referred to as DI processing). Lubricant is applied to the metal surface during this molding operation, and the aluminum powder (smut) adheres to the inner wall of the resulting container, so the lubricant or smut is generally applied before chemical conversion treatment. Is removed from the metal surface, cleaned, and protected by metal conversion treatment and painting.

In recent years, the outer diameter of the can lid has been reduced from 206 (6.0 cm) to 204 (about 5.7 cm) to reduce costs.
Further, the diameter is being reduced to 202 (about 5.4 cm). In order to cope with this, the diameter of the upper portion of the container must be reduced, and the upper drawing process (necking process) of the painted can is becoming severe. In this reduced diameter can, higher coating film adhesion is required.

[0008]

Problems to be Solved by the Invention
-39314, "Surface treatment method for aluminum"
Since the surface treatment bath used for the above does not contain an agent for removing the oxide film formed on the metal surface from the metal surface, a chemical conversion film is formed on the oxide film. In such a case, since the chemical conversion film becomes non-uniform, it is necessary to increase the thickness of the chemical conversion film in order to satisfy corrosion resistance such as boiling water and retort properties. However, when the thickness of the chemical conversion coating is increased, the adhesion between the coating and the metal surface during necking, that is, the coating adhesion, becomes insufficient. On the other hand, if the adhesion of the coating film is to be satisfied, the chemical conversion film must be made thinner, and the corrosion resistance becomes insufficient because the chemical conversion film is non-uniform.

On the other hand, the fluoride contained in the "coating solution for metal surface" disclosed in JP-B-56-33468 can etch an oxide film formed on a metal surface and release the oxide film from the surface. However, the metal surface is oxidized again because there is no agent for taking in oxygen contained in the detached oxide film. Therefore, as described above, a chemical conversion film is formed on the oxide film,
The conversion coating becomes non-uniform. If the corrosion resistance is to be satisfied in a state where the uniformity of the chemical conversion film is insufficient, the thickness of the chemical conversion film is increased, and the adhesiveness of the coating film becomes insufficient. On the other hand, in order to satisfy the coating film adhesion, it is necessary to reduce the thickness of the chemical conversion coating, and the chemical conversion coating is in an uneven state, so that the above-mentioned corrosion resistance becomes insufficient.

That is, it has been difficult to achieve both the corrosion resistance and the coating film adhesion to the reduced diameter can by the conventional surface treatment method and the like.

The present invention has been made in view of the above conventional problems, and an object thereof is to form a thin film having high uniformity and to form a protective film having a good appearance, anticorrosion property, and coating adhesion. A metal-based metal surface treating composition, a treating bath, and a treating method.

[0012]

In order to achieve the above-mentioned object, the composition for treating an aluminum-based metal surface of the present invention comprises at least one of phosphoric acid, condensed phosphoric acid or salts thereof.
A seed and at least one of a zirconium salt or a titanium salt,
In the composition containing a fluoride, at least one kind of phosphorous acid, hypophosphorous acid or salts thereof is further contained.

A treatment bath is prepared by diluting the aluminum-based metal surface-treating composition of the present invention with an appropriate amount of water to a concentration within the range of use, whereby the metal surface is coated with a chemical conversion film (ie, surface treatment). If you do)
The fluoride contained in the surface treatment composition of the present invention etches the oxide film formed on the metal surface, and separates the oxide film from the surface. The phosphorous acid, hypophosphorous acid or salts thereof contained in the surface treatment composition of the present invention act as a reaction accelerator. That is, it is considered that these act as a reducing agent and can prevent the oxidation of the metal surface as much as possible. Furthermore, a double salt is formed by the zirconium salt and / or titanium salt in the treatment bath, the fluoride, phosphoric acid and / or condensed phosphoric acid, and phosphorous acid and / or hypophosphorous acid, whereby a double salt is formed. Form a strong film on the metal surface.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum-based metal surface treatment composition of the present invention comprises at least one selected from phosphoric acid, condensed phosphoric acid or salts thereof, at least one selected from zirconium salts or titanium salts, and a fluoride. In a composition containing,
Furthermore, phosphorous acid (H ₂ PHO ₃ ), hypophosphorous acid (HPH
₂ O ₂ ) or at least one of salts thereof.

Examples of phosphoric acid and phosphate include H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ and NaH ₂ PO.
₄ , alkali metal phosphates such as KH ₂ PO _4, alkaline earth metal phosphates such as calcium phosphate and magnesium phosphate, and the like. The condensed phosphoric acid includes, for example, pyrophosphoric acid, tripolyphosphoric acid, metaphosphoric acid, ultraphosphoric acid, and the like, and the salt of condensed phosphoric acid includes, for example, alkali metal salts such as sodium and potassium, and alkali such as calcium and magnesium. Examples thereof include earth metal salts and ammonium salts.

Examples of the zirconium salt include lithium, sodium, potassium and ammonium salts (Li ₂ ZrF ₆ , Na ₂ ZrF ₆ , K ₂ ZrF) of zirconium hydrofluoric acid (H ₂ ZrF ₆ ) and fluorozirconic acid.
₆ , (NH ₄ ) ₂ ZrF ₆ ), zirconium sulfate (Zr
(SO ₄ ) ₂ ) and zirconyl sulfate (ZrO (S
O ₄ )), zirconium nitrate (Zr (NO ₃ ) ₄ ), zirconyl nitrate (ZrO (NO ₃ ) ₂ ), zirconium acetate, zirconium fluoride (ZrF ₄ ), and the like.

Examples of the titanium salt include lithium, sodium, potassium and ammonium salts of titanium hydrofluoric acid and fluorotitanic acid (Li ₂ TiF ₆ , Na ₂ Ti).
_{F 6, K 2 TiF 6,} (NH 4) 2 TiF 6), titanium sulfate _{(Ti (SO 4) 2)} , titanyl sulfate (TiO (S
O ₄ )), titanium nitrate (Ti (NO ₃ ) ₄ ), titanine nitrate (TiO (NO ₃ ) ₂ ), titanium fluoride (TiF ₃
· TiF _4), and the like can be given.

Examples of the fluoride include hydrofluoric acid (HF), ammonium fluoride (NH ₄ F), ammonium hydrogen fluoride (NH ₄ HF ₂ ), sodium fluoride (NaF), sodium hydrogen fluoride ( NaHF ₂ ) and the like.

As salts of phosphite and hypophosphite,
Examples thereof include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, and ammonium salts.

The aluminum-based metal surface treatment bath is
It is obtained by diluting the above-mentioned aluminum-based metal surface treatment composition with a suitable amount of water to a concentration within the range of use. Hereinafter, description will be given based on an aluminum-based metal surface treatment bath (hereinafter referred to as "treatment bath").

At least one of phosphoric acid or condensed phosphoric acid or a salt thereof is at least 10 ppm in terms of phosphoric acid, preferably 10 to 500 pp in the treatment bath of this embodiment.
m, more preferably 10 to 100 ppm.
When at least one of phosphoric acid or condensed phosphoric acid or a salt thereof is less than 10 ppm in terms of phosphoric acid in the treatment bath, boiling water resistance to blackening occurs, while when phosphoric acid or the like is large,
Since boiling water resistance to blackening occurs and the adhesion of the coating film deteriorates, it is preferably within 500 ppm in terms of phosphoric acid.

At least one of zirconium salt and titanium salt is contained in the treatment bath of the present embodiment in an amount of at least 10 ppm, preferably 10 to 500 ppm, and more preferably 10 to 100 ppm in terms of metal. When at least one of the zirconium salt and the titanium salt is less than 10 ppm in terms of metal in the treatment bath, almost no chemical conversion film is formed. On the other hand, addition of a large amount of zirconium salt or the like to the treatment bath does not improve the effect, so it is 500 p
It is preferably within pm.

The effective fluoride content in the treatment bath of this embodiment is at least 1 ppm in terms of fluorine, preferably 3 to.
50 ppm is contained. If the effective fluoride is less than 1 ppm in terms of fluorine in the treatment bath of the present embodiment, the etching of the surface of the aluminum-based metal hardly occurs, so that the aluminum-based metal (including aluminum, aluminum alloy, etc.) The adhesion between the surface and the film decreases.
On the other hand, when the content of fluoride is high, not only the film formation becomes difficult because the etching rate is faster than the film formation rate, but also the boiling water resistance to blackening and the coating adhesion decrease. It is preferably within 50 ppm in terms of fluorine.

Here, the effective fluoride refers to a fluoride that liberates fluorine ions in the treatment bath, and the free fluorine ion (F ⁻ ) in this treatment bath is hereinafter referred to as “effective fluoride ion”. The concentration of this effective fluorine ion can be determined by measuring the treatment bath or the like with a meter having a fluorine ion electrode. In addition to etching the oxide film on the aluminum surface, the available fluorine ions have a function of stopping or preventing the precipitation of zirconium and / or titanium phosphate in the treatment bath. Furthermore, it also has the function of dissolving aluminum dissolved in the treatment bath during the aluminum surface treatment as a complex in the treatment bath to control or prevent adverse effects in the surface treatment process.

At least one of phosphorous acid, hypophosphorous acid and salts thereof is at least 10 ppm, preferably 10 to 5000 ppm in terms of phosphorous acid or hypophosphorous acid in the treatment bath of this embodiment. , More preferably 50-
500 ppm is contained. At least one of phosphorous acid, hypophosphorous acid or salts thereof is added to the treatment bath of the present embodiment,
When the phosphorous acid conversion or hypophosphorous acid conversion is less than 10 ppm, the uniformity of the chemical conversion coating becomes insufficient, and when the concentration of phosphorous acid or the like in the treatment bath is high, the coating film adhesion decreases. Therefore, 5000 pp in terms of phosphorous acid conversion or hypophosphorous acid conversion
It is preferably within m.

The aluminum-based metal surface-treating composition of the present invention and the material to be treated in the treatment bath are aluminum and / or aluminum alloys. Examples of the aluminum and / or aluminum alloy include aluminum, aluminum-copper, aluminum-zinc, aluminum-manganese, aluminum-magnesium, aluminum-magnesium-silicon, aluminum-zinc-
Examples include magnesium. Further, the shape of the target material may be a plate shape, a bar shape, a line, a tube, and can be applied to a beverage can or the like.

The treatment bath of this embodiment is used on the acidic side. The pH of the treatment bath is 1.5 to 4.0, preferably 2.
0 to 3.5. When the pH of the treatment bath is less than 1.5, not only etching becomes excessive and it becomes difficult to form a coating film, but also the blackening resistance to boiling water resistance and the coating film adhesion are lowered. On the other hand, when the pH of the treatment bath exceeds 4.0, the treatment bath becomes cloudy and sludge is generated. In addition, since a film is hardly formed, boiling water black resistance is reduced.

The treatment temperature of the aluminum-based metal surface treatment method of the present embodiment (hereinafter referred to as "treatment method") is from room temperature to 60.
° C, preferably 30 to 50 ° C. If the treatment temperature is lower than room temperature (for example, 25 ° C.), the film formation rate is low, and the concentration is high, which is economically disadvantageous. When the treatment temperature exceeds 60 ° C., the treatment bath becomes cloudy and sludge is liable to be generated. Further, a large amount of energy is required for maintaining the temperature, which is economically disadvantageous.

The treatment time of the treatment method of the present embodiment varies depending on the treatment composition, the treatment temperature and the treatment method, but is generally 5 to 60 seconds, and the treatment method of the present embodiment is the treatment bath described above. The aluminum product or the like may be dipped therein, or the treatment bath may be treated by a known method such as spraying or coating on the aluminum product or the like.

Further, other preferable embodiments of the present invention other than those described in the claims will be shown below.

1. The aluminum-based metal surface treatment bath contains at least one phosphoric acid, condensed phosphoric acid or a salt thereof in an amount of 10 to 500 ppm in terms of phosphoric acid and at least one zirconium salt or a titanium salt in an amount of 10 to 500 in terms of a metal.
ppm and 1 to 50 ppm of effective fluoride in terms of fluorine
And at least one of phosphorous acid, hypophosphorous acid or salts thereof in terms of phosphorous acid or hypophosphorous acid of 10 to 50.
And 00 ppm.

2. The aluminum-based metal surface treatment bath contains at least one phosphoric acid or condensed phosphoric acid or a salt thereof in an amount of 10 to 100 ppm in terms of phosphoric acid, and at least one zirconium salt or a titanium salt in an amount of 10 to 100 in terms of a metal.
ppm and effective fluoride in terms of fluorine of 3 to 20 ppm
And at least one of phosphorous acid, hypophosphorous acid or salts thereof in a phosphorous acid conversion or hypophosphorous acid conversion of 50 to 50.
And 0 ppm.

3. At least one of phosphoric acid, condensed phosphoric acid or salts thereof, at least one of zirconium salt or titanium salt, fluoride, and at least one of phosphorous acid, hypophosphorous acid or salts thereof, A method for treating an aluminum-based metal surface, which comprises forming a treatment bath using the contained aluminum surface treatment composition and immersing the aluminum product in the treatment bath.

4. At least 10 ppm of phosphoric acid or condensed phosphoric acid or salts thereof in terms of phosphoric acid
And at least one zirconium salt or titanium salt in terms of metal of at least 10 ppm, an effective fluoride of at least 1 ppm in terms of fluorine, and phosphorous acid, hypophosphorous acid or at least one of salts thereof in phosphorous acid. An aluminum-based metal surface treatment method comprising immersing an aluminum product in an aluminum-based metal surface treatment bath containing at least 10 ppm in terms of conversion or hypophosphorous acid conversion.

5. PH of aluminum metal surface treatment bath
Is 1.5 to 4.0.

6. The treatment temperature of the aluminum-based metal surface treatment method is from room temperature to 60 ° C.

[0037]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

Examples 1 to 18 and Comparative Examples 1 to 6 (1) Object to be treated: 3004 alloy aluminum plate was DI
A lidless container to which lubricating oil and smut adhered was used.

(2) Detergent: An acidic detergent "Surf Cleaner NHC250" manufactured by Nippon Paint Co., Ltd. was used.

(3) Treatment conditions: The above-mentioned container was spray-treated with the above-mentioned detergent at 75 ° C. for 60 seconds to remove the lubricating oil and smut, and then spray-washed with tap water for 15 seconds. The treatment liquid of the treatment bath shown was sprayed. Then, it was spray-washed with tap water for 15 seconds and deionized water for 5 seconds, and then dried at 200 ° C. for 2 minutes.

(4) Detergency evaluation: The following items were tested. Table 3 shows the results.

(A) Boiling water black denaturation: The bottom portion cut out from a treated DI processing container (hereinafter referred to as "treatment can") was immersed in boiling tap water at 100 ° C for 30 minutes, and the degree of blackening was observed. did. The following five grades were evaluated according to the degree of blackening.

◎: No black discoloration ○: Slight black discoloration △: Light black discoloration ×: Significant black discoloration × ×: Complete black discoloration (b) Retort resistance: Pressurized tap water in the pressure cooker to 12
The treatment can was placed in the steam section at 5 ° C. for 30 minutes, and the degree of whitening was observed. The following five levels were evaluated according to the degree of whitening.

◎: No whitening at all ○: Slight whitening Δ: Light whitening ×: Fair whitening × ×: Complete whitening (c) Adhesion of coating film: Aqueous white paint is applied to the outer surface of the treated can, A clear paint (epoxy-modified acrylic clear paint) was applied on top, baked and dried to give a test piece. Evaluation of coating film adhesion was performed by bending (wedge bending method). As shown in FIG. 1, the evaluation method of the coating film adhesion is 3 ° from 0 mmφ at the tip.
4m at 80mm from this tip
After bending so that it becomes mφ (see FIG. 2), as shown in FIG. 3, attach the tape to the bent portion, then peel the tape (peeling in the direction of the white arrow in FIG. 3) and peel the tape. It is a method of evaluation by the peeling length (mm) of the coating film from the tip when the coating is applied. The shorter the peel length of the coating film, the better the coating film adhesion.

The evaluation results are shown below.

[0046]

[Table 1]

[Table 2]

[Table 3] From these results, according to the aluminum-based metal surface treatment composition, the treatment bath and the treatment method of the present invention, a highly uniform coating film is formed in a thin film, and the appearance, anticorrosive property and coating film adhesion are also conventional. It was found to be improved compared to.

[0047]

As described above, according to the aluminum-based metal surface treatment composition, the treatment bath and the treatment method of the present invention, a thin film having high uniformity can be formed. It is possible to provide a protective coating which is remarkably excellent and is also excellent in boiling water blackening resistance and retort resistance.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a bent state of a test piece used for evaluation of coating film adhesion.

FIG. 2 is a perspective view of the bent test piece shown in FIG. 1 as viewed from the back.

FIG. 3 is a diagram illustrating a method for testing coating film adhesion.

Claims (3)

[Claims] 1. A composition comprising at least one of phosphoric acid, condensed phosphoric acid or salts thereof, at least one of zirconium salt or titanium salt, and fluoride, further comprising phosphorous acid, A composition for treating an aluminum-based metal surface, which comprises at least one of phosphorous acid and salts thereof. 2. At least 10 ppm of phosphoric acid, condensed phosphoric acid or salts thereof in terms of phosphoric acid.
And at least one of zirconium salt or titanium salt in terms of metal of at least 10 ppm, effective fluoride of at least 1 ppm in terms of fluorine, phosphorous acid, hypophosphorous acid or at least one of salts thereof, phosphorous acid. At least 10p in terms of conversion or hypophosphorous acid conversion
pm, and an aluminum-based metal surface treatment bath comprising: 3. At least one of phosphoric acid, condensed phosphoric acid or salts thereof, at least one of zirconium salt or titanium salt, fluoride, and at least phosphorous acid, hypophosphorous acid or salts thereof. A method for treating an aluminum-based metal surface, which comprises forming a treatment bath using a composition for treating an aluminum surface containing one kind and contacting the treatment bath with an aluminum product.